Currently used methods for preparing lasts, i.e., anatomical models of the human foot for use in constructing custom footwear, generally involve first creating a plaster mold (i.e., negative impression) of the foot; then creating a plaster positive of the foot from the plaster negative; and lastly, having a skilled artisan hand-carve a wooden last using the plaster positive as a model. Alternatively, the artisan will use the plaster positive to modify a pre-formed last by carving material from, or adding material to, the pre-formed last in order to conform it to the plaster positive. See, e.g., J. E. Bishop, "If the Shoe Fits, It's Probably Been Mostly Luck Until Now", Wall Street Journal, Mar. 1, 1985, which describes the "primitive technology" currently used for making orthopedic shoes. As a result of this painstaking and cumbersome method, lasts that are used to make custom-fitted shoes generally cost at least hundreds of dollars each and can take weeks, if not months, to prepare.
The preparation of lasts by these artisans is estimated to represent fifty to seventy-five percent of the cost and effort involved in constructing custom footwear. Furthermore, the number of artisans skilled at such work is decreasing significantly, at a time when the elderly population is increasing the demand for custom footwear. As a result, many patients requiring custom orthopedic footwear do not have access to last designers, or simply cannot afford such footwear.
As discussed in the Bishop article, a promising approach for the future may be the use of computer-aided design and computer-aided manufacturing of custom footwear. See, e.g., "A Proposed Design for an Orthopedic Footwear CAD/CAM Delivery System", which is described as a "Report of Workshops to Define the Clinical and Engineering Criteria for a Computer-Aided Design and Manufacturing System for Orthopedic Footwear", prepared by Research Triangle Institute, D. J. Rouse, Project Director. As proposed, this approach would involve making a digital scan of a foot and using that information to carve a last on a computer-aided lathe. The affordability and feasibility of such an approach however remain to be proven. In light of the ever-increasing demand for orthopedic footwear, there exists a current and urgent need for a quick, inexpensive and effective method for preparing anatomically accurate lasts.